A The Health Effects of Occupational Exposure to Asphalt Fumes Introduction

the asphalt roofing industry science & medical group
a health and safety information coalition
R
U
P
The Health Effects of Occupational Exposure
to Asphalt Fumes
A Review of the available Scientific Data
and On-Going Industry and Government Research
Introduction
A
sphalt, a familiar and commercially important commodity, is a solid or semisolid thermoplastic material defined by the American Society of Testing Materials as a dark brown to
black cementitious substance, consisting predominantly of bitumens, which occurs in na-
ture or, more commonly, is produced by the refining of petroleum crude oils.(1) Because of its
valuable properties, including adhesive characteristics, flexibility, durability, water resistance, high
dielectric strength, and ability to form strong cohesive mixtures with mineral aggregates,(1)asphalt
has been used extensively for over 5,000 years in pavement construction, roofing, waterproofing
and other industrial applications.(2)
In the United States today, asphalt is used primarily in road paving and in the roofing industry,
where it is found in such popular products as built-up roofing and modified bitumen roofing
Asphalt Roofing
Manufacturers
Association
systems, asphalt shingles, and roof coatings, mastics and cements. Occupational exposure to asphalt fumes can occur in those operations in which asphalt is heated to high temperatures (well
above 100°F)such as in plants manufacturing roofing asphalt products and during the installation
of built-up roofing (BUR) systems. Asphalt shingles, coatings, mastics and cements (none of which
are heated to high temperatures during installation), as well as other asphalt products (such as
National Roofing
Contractors
Association
BUR) which have cooled after installation, do not release fumes.
Asphalt fumes contain trace levels of unsubstituted polynuclear aromatic hydrocarbons (PAHs),
some of which have been shown to cause skin cancer in laboratory tests on experimental animals.
The National Institute for Occupational Safety and Health (NIOSH) has concluded, however, that
the presence of these very small concentrations of PAHs in asphalt fumes does not present a sig-
Asphalt Institute
nificant risk of cancer to workers.
(3)
As a result, existing worker health recommendations for as-
phalt fumes are based on the acute, reversible eye and respiratory tract irritation some exposed
workers may experience.
(3)
Specifically, existing guidelines published by NIOSH
Roof Coatings
Manufacturers
Association
ernmental Industrial Hygienists (ACGIH)
( 4)
and the American Conference of Gov-
recommend that workplace exposures to asphalt fumes
be kept below 5.0 mg/m3 to protect against acute eye and respiratory irritation. Likewise, while
the Occupational Safety and Health Administration (OSHA) has not set a legal standard for workplace asphalt fume exposure, a 1992 OSHA proposal to establish a 5.0 mg/m3 limit to protect against
(5)
irritation effects is pending( 5 ) .These recommendations are not identical because they are based on
different methods of measuring fume exposure levels. But regardless of which method is used,
Doc# AF- WP-0195
the health effects of occupational exposure to asphalt fumes:
A Review of the Available Scientific Data and On-Going Industrial and Government Research
Introduction
continued
occupational fume exposures during the manufacture and application of asphalt roofing products today are generally well below the current guidelines.
(6)
In recent years, studies published in the United States and Europe have raised new questions about the possible carcinogenic properties of asphalt fumes as well as the potential for
respiratory and other irritation effects at lower exposure levels.
(5,7) These
reports, in turn, have
prompted industry, government and other organizations to launch a number of new studies to
explore these questions and to identify exposure reduction controls that can be promptly
implemented in the event new hazards are documented by sound scientific evidence. The
purposes of this paper are to provide an up-to-date review of the available scientific evidence
on the health effects of occupational exposure to asphalt fumes and to describe the ongoing
government and industry research programs.
I
Potential
Carcinogenity
(a)
Epidemiologic
Studies
B
ecause epidemiologic studies of exposed human populations provide the best scientific evidence of whether environmental agents pose health hazards, and because of
the widespread use of asphalt in industry, many attempts have been made to investi-
gate the cancer experience of workers potentially exposed to asphalt. Unfortunately, these
investigations for a number of reasons have not yielded definitive results.
(8,9)
The most recent authoritative review of the available epidemiological data is a 1994 paper
written by the International Agency for Research on Cancer (IARC), whose carcinogenicity
evaluations frequently form the basis for regulatory decisions in the U.S. and elsewhere. Based
on a comprehensive and critical review of the epidemiologic literature, IARC finds no basis to
(10)
The IARC review concludes,
conclude that exposure to asphalt fumes poses a cancer .(10)
sk.
specifically, that the published studies either fail to reveal increased rates of cancer among
asphalt workers or have methodological limitations which render them unreliable as a basis
for scientific evaluation. According to IARC, a frequent problem, particularly in European
studies, has been what epidemiologists call “confounding” due to co-exposure to coal tar and
other recognized human carcinogens.
The Hansen studies of Danish mastic asphalt workers(11,12,13) are good examples of the limitations in the available epidemiological data discussed in the IARCIAR
C review. The Hansen studies, published in 1989 and 1991, raised new questions about the carcinogenicity of asphalt
fumes because they found increased risks of lung and digestive tract cancers among study
populations of workers in Denmark’s mastic asphalt industry. As used in Denmark, the term
"mastic asphalt" refers to a low-volume specialty asphalt product which is applied by workers
on their hands-and-knees at very high temperatures. (9,14) Neither the composition of mastic
asphalt, nor the work practices used in its application, bear any resemblance to the manufacture or installation of asphalt roofing or paving materials in the U.S.
Methodological questions have been raised about various aspects of the Hansen studies,
including: the absence of adequate exposure data on asphalt fumes and possible confounders;
possible selection bias in the cohort definition and enumeration; indications of a reverse
2
the health effects of occupational exposure to asphalt fumes:
A Review of the Available Scientific Data and On-Going Industrial and Government Research
dose-response trend for lung cancer; and questionable statistical adjustments to separate-out
the effects of smoking and coal tar exposures.(8,15,16) In addition, the striking differences be-
Epidemiologic
Studies
tween the morbidity and mortality patterns of Hansen’s cohorts and those of U.S. asphalt
workers recently studied
(17, 18)
I suggest that non-work-related lifestyle factors may have played
an etiological role in the results. Thus, the only U.S. regulatory agency to evaluate the Hansen
studies to date has found them inconclusive due to such methodological concerns.
.
(16)
Coal tar confounding also undermines the Hansen findings, as the recent I A R C review
concludes. In fact, I A R C ' finding that Dr. Hansen’s study subjects were significantly exposed
to coal tar is supported by a large and persuasive body of evidence, including
:
(i) Danish
(14,,19,20,21)
)
highway department records;
(ii) contemporaneous formulations for mastic asphalt
pavement products obtained from their h
Danis
(14, 20)
manufacturers;
(iii ) confirmation by
(19,21)
Danish highway department officials based on long-term service and governmen
t
records;
(20, 21)
(iv) chemical analyses of randomly selected mastic asphalt pavemen
t
samples;
limited industrial hygiene sampling data .
(21)
and (v)
Accordingly, Dr. Hansen has effectively acknowl-
edged the prior use of coal tar and the need to reassess her findings.(22)
In spite of the failure of previous epidemiologic investigations to produce a definitive answer, there remains much interest in such studies as a longer-term research tool. Several years
ago, the Asphalt Institute commissioned an assessment of the feasibility of conducting a retrospective epidemiologic study of workers employed in the U.S. asphalt industry in previous
years. The investigators found, however, that such a study would be infeasible in large part
due to the absence of adequate documentation of historical exposures and the known pres-
ence of potential confounders such as smoking.(23) I A R C is in the process of evaluating the
feasibility of a study of European asphalt workers,(24)and recently made available for comment
(25)
a proposed study protocol which I A R C projects can be completed in six years.
The U.S. asphalt
industry has provided financial support as well as logistical assistance for this initiative.(26)
In addition, two large U.S. asphalt roofing product manufacturers are conducting mortality
surveillance programs to track the health experience of their workers. Over the 25 years of
experience included in these two ongoing programs, no evidence of an increased risk of cancer among asphalt roofing manufacturing workers has emerged, although more time is needed
before scientifically sound conclusions can be drawn.
(27,28)
(b)
Toxicological
Research
T
he primary source of the renewed scientific interest in the possible carcinogenicity of
asphalt fumes arises from two NIOSH skin-painting bioassays of experimental mice.
(29,30)
These studies involved roofing asphalt fume condensates that were specially prepared
according to a novel laboratory procedure. In the first study, laboratory fume condensates
(29,31)
generated at 450° and 600°F (232° and 316°C) produced skin cancers in the test mice.
In the
second, laboratory fume condensates generated at 600°F (316°C) were separated into five fractions (labeled A through E), which were then bioassayed alone and in various combinations.
The second study found that the carcinogenic activity of the laboratory test materials was
restricted to Fractions B and C, which contained significant concentrations of alkylated
3
the health effects of occupational exposure to asphalt fumes:
A Review of the Available Scientific Data and On-Going Industrial and Government Research
3- to 7-ring polynuclear aromatic compounds (PACs), including aromatic hydrocarbons as well
Toxicological
Research
as sulfur and oxygen heterocycles. NIOSH and industry scientists have theorized that these
large and diverse families of chemicals may well contain the subset of compounds responsible
(30)
for the dermal carcinogenicity NIOSH found in the test mice.
Although Fractions B and C
represent a small portion of the total laboratory fume condensate (about 13%), they contain
many individual compounds that have not yet been specifically identified. Thus, as NIOSH
has acknowledged, the source of the dermal carcinogenicity seen in the NIOSH mouse studies
continues to elude us.
(30)
Nevertheless, the NIOSH laboratory fume mouse studies have raised questions about whether
there is a possible cancer risk to workers exposed to the asphalt fumes created in real-world
manufacturing and application operations. In response, the U.S. asphalt industry, including
organizations representing asphalt manufacturers as well as paving and roofing companies,
formed in 1989 a coalition known as the Asphalt Industry Environmental Oversight Committee (AIEOC) to sponsor and conduct additional scientific research to find the answers left open
by the NIOSH mouse studies.
The early phases of the AIEOC research program have focused on the question of the representativeness of NIOSH's laboratory test sample. In investigating this subject, industry scientists have relied heavily on standard chemical characterization techniques and short-term
biological tests, particularly the Modified Ames bacterial mutagenicity assay, which has been
shown to have a very high correlation with the dermal carcinogenicity of some complex petroleum-derived materials in mouse skin-painting studies.
(32, 33)
Early on, the program revealed a
positive, although imperfect, correlation between mutagenicity as measured by the Modified
Ames assay and the carcinogenicity of the five laboratory fume condensate fractions bioassayed in the second NIOSH study.
(34)
Subsequent phases of the industry research on the representativeness of fume samples
reveal that the laboratory-generated fume condensates used in the NIOSH mouse studies are
markedly different, both chemically and toxicologically, from the asphalt fumes that are created under actual operating conditions in the field. These differences appear to arise from
several specific elements of the NIOSH laboratory fume generation procedure, including: (i)
vigorous stirring of a small (8 to 10 liter) sample of asphalt at 200-300 revolutions per minute;
(ii) use of a vacuum pump to pull a pre-heated (100°C) air stream across the sample at a rate of
IO liters
per minute; and (iii) continuous heating of the same sample under these stirring and
vacuum conditions for extended periods ranging from 4 to 14 hours.
(29,30,31)
None of these conditions in the NIOSH laboratory procedure exists during fume generation in actual asphalt industry operations. In real production and application operations, asphalt is not heated for extended periods, vigorously agitated, or used in conditions of significant
vacuum. Basic principles of physical chemistry hold that severe laboratory processing conditions like those used in the NIOSH studies would have the effect of causing larger, more complex and much less volatile compounds, including alkylated and heterocyclic 3- to 7-ring
(35)
PACs, to evolve from the parent asphalt into the laboratory fume test sample.
In fact, indus-
try-sponsored compositional testing has empirically confirmed that both vigorous mechanical
agitation, and the use of vacuum, substantially alter fume chemistry in precisely the fashion
(36)
predicted by theoretical principles.
nciples. (36)pri
4
the health effects of occupational exposure to asphalt fumes:
A Review of the Available Scientific Data and On-Going Industrial and Government Research
More importantly, two independent studies of a variety of field fume samples, derived
from materials, temperatures and operations typical of asphalt paving and roofing work in the
U.S., have recently been reported. (36,37,38) In each case, the composition of the field fume sample
Toxicological
Research
was compared to a companion laboratory sample generated by applying the NIOSH laboratory
protocol to the same parent asphalt, and at the same temperature, used in the field sample.
In all cases, the laboratory-generated samples contained heavy concentrations of higher
molecular weight chemical species, including 3- to 7-ring PACs , while the counterpart field
(36,37,38)
samples contained little or no detectable levels of such com po unds. .
In one of the two
studies, the fume samples were subjected to Modified Ames mutagenicity assays; the labora(38 )
tory samples tested positive, while the field samples tested neg ative.
These results are con-
sistent with other studies finding mutagenic activity in laboratory-generated paving and roofing
asphalt fume condensates, but not in field fumes generated from the same parent asphalts at
(34,39 )
standard manufacturing and application tem pe rature s .
Also significant is the repeated finding in these studies that the chemical composition of
the field samples bears a strong resemblance to that of Fraction A in the second NIOSH mouse
skin-painting study. If anything, actual field fumes appear to be more volatile, and contain
even lower concentrations of 3- to 7-ring PACs , than NIOSH Fraction A.. (36,37,38) This finding is
further ground for cautious optimism that field fumes will not be shown to possess the carcinogenic properties of Fractions B and C of NIOSH's laboratory fume condensate sample. Thus,
despite the presence of low concentrations of
3-to 7-ring PACs and sulfur heterocycles, Frac-
tion A showed no evidence of carcinogenicity when bioassayed alone, and showed no evidence of carcinogenic, synergistic, co-carcinogenic or tumor promotion effects in a dozen other
mouse skin-painting bioassays conducted in the second NIOSH study, in which Fraction A
(30 )
was applied in combination with one or more of the other fractions or ben zo[a]pyrene (B[a]P).
Presently, research in the chemistry and toxicology areas is designed to shed light on the
scientific questions that cannot be answered definitively by the available data: First, what
compounds or families of compounds in Fractions B and C of the NIOSH laboratory-generated
fume condensate are likely responsible for the mouse skin cancers? Second, considering the
great compositional variability of asphalts and asphalt fumes, are such compounds present in
any, some, or most field fumes? And third, if so, are they present in sufficient quantities to
warrant concern about a cancer risk to exposed workers? Parallel studies being conducted by
industry and NIOSH, in consultation with Organized Labor, are underway to get prompt an(40,41)
swers to these questions. (40,41) In the absence of adequate epidemiologic studies or experimental rodent bioassays, the ongoing work utilizes chemical characterization and short-term
biological tests, including the Modified Ames assay, which can quickly generate relevant
scientific data.
The basic approach in these research programs is to subdivide Fractions B and C into ever
smaller subfractions in an effort to isolate the source of the activity reported by NIOSH in
laboratory-generated fumes. Once a smaller group of suspect compounds has been isolated by
applying compositional and short-term biological tests to the subfractions, it will be possible
to look for these compounds in field fumes and test them for the presence of biological activity. Industry and NIOSH scientists are meeting on a regular basis to share and discuss the
results of their research as well as future experimental protocols.
4
The Health Effects of Occupational Exposure to Asphalt Fumes:
a review of the available scientific data and on-going industry and government research
Toxicological
Research
continued
In a separate initiative designed to overcome the serious questions that remain about the
representativeness of the NIOSH laboratory fume generation technique, industry researchers
have developed an alternative laboratory fume generation procedure that better simulates
field exposures. Such a procedure might be used, for example, for chemical or biological tests
requiring greater quantities of fumes than can practicably be collected in actual field operations. The equipment and protocol for this new procedure has been provided to IARC, which
will use them in connection with its ongoing study in Europe.
II
Research on
Exposure
Measurement
and Control
Techniques
0
2
ngoing research on the health effects of asphalt fumes is not limited to possible carcinogenic effects. Also being examined are the potential pulmonary and other irrita
tion effects, which, as noted above, form the basis of the 5.0 mg/m
exposure limits currently recommended by NIOSH
(5)
0SHA.
(26)
(3)
and ACGIH
(4)
3
asphalt fume
and recently proposed by
These effects have recently become the subject of renewed scientific attention as a
result of the Norseth study of Norwegian asphalt paving workers.(42)
The Norseth study finds statistical correlations between asphalt fume concentrations and
subjective employee reports of symptoms such as fatigue and eye and throat irritation, and
3
recommends, among other things, that workplace fume exposures be kept below 0.4 mg/m ,
measured as the benzene soluble fraction of total particulate. A U.S. asphalt industry scientific
review and investigation of the Norseth study has concluded that additional research and data
analysis are needed in order to better understand the potential for acute pulmonary and other
irritation effects among U.S. asphalt workers, and to adequately investigate other possible
environmental and industrial causes of any such effects.
(43,44)
Several different initiatives are underway to explore the ramifications of Norseth’s findings. First, U.S. asphalt industry scientists have proposed a collaboration with Dr. Norseth and
his colleagues in Norway to reevaluate the exposure-response correlations in the Norseth data,
using more sophisticated statistical tools and including a large pool of data that was excluded
in the report of the Norseth study that was published in 1991.
Second, the asphalt industry has launched a similar study of U.S. workers, which has now
entered its third phase and is expected to be completed in about a year. Results from the first
two phases, although preliminary and not yet published, do not reveal adverse respiratory
3
irritation effects at typical workplace exposure levels of approximately I .o mg/m and below
(measured as benzene soluble fraction). The data are, of course, subject to reevaluation after
completion of the third phase, and workers with higher exposures are needed to reliably
establish a no-observed-effect level. In addition, an ongoing NIOSH-Federal Highway Administration (FHWA) study of crumb-rubber-modified (CRM) paving asphalts is examining the
potential for acute respiratory irritation effects in conventional asphalt paving operations as
well as CRM jobs.
(41)
Industry epidemiologists and industrial hygienists have been consulting
with NIOSH researchers on the design and implementation of both the AIEOC and NIOSHFHWA studies.
6
The Health Effects of Occupational Exposure to Asphalt Fumes:
a review of the available scientific data and on-going industry and government research
Through these and other efforts, a much better understanding of the acute respiratory
irritation risks to asphalt workers, as well as data that will permit scientists to isolate the
specific causes of any such effects from the numerous environmental agents that could be
(43,44)
responsible,
T
may be available within a year or so.
III
he U.S. asphalt industry, in consultation with Government and Organized Labor, has initiated several efforts to identify fume exposure reduction techniques that can be promptly
implemented should the ongoing health effects studies identify a need to reduce expo-
sures below their current levels. The first step in this area of research was an industry-sponsored cross-sectional exposure study, which was completed in 1991 This study demonstrated
worker exposures in all sectors of the asphalt industry to be well-controlled, with typical
exposures falling well below current recommended limits.
(6)
Acute
Pulmonary
and Other
Irritation
Effects
Recently, asphalt roofing industry representatives initiated discussions with roofing kettle
manufacturers to identify ways of modifying roofing kettles to lower exposures even further,
and are actively participating in a study recently announced by NIOSH to identify feasible
means of lowering fume exposures in roofing operations.
(41, 46)
(45)
Similar efforts are underway in
the paving sector.
U.S. asphalt industry scientists are also actively working on a program to develop an improved and standardized methodology for measuring asphalt fume concentrations in the workplace. Historically, occupational exposures to asphalt fumes have been evaluated by collecting
air samples using several, somewhat different benzene soluble fraction (BSF) methods devel(47)
oped to measure coal tar pitch volatiles (specifically, OSHA Method 58
5023(48))
or using the total particulate method (NIOSH Method 0500
and NIOSH Method
(49)
) The BSF method,
which measures the organic component of the fume, is regarded by many industrial hygienists as a more appropriate index of potential health effects because of asphalt’s organic nature.
The total particulate method captures airborne particulates other than asphalt fume droplets,
and measures inorganic materials that are not considered likely to play a role in potential
asphalt-related toxicity.
A scientific evaluation of the two BSF methods specifically addressing asphalt fume exposure assessment has recently been completed by U.S. asphalt industry scientists. The 1995
report on this study concludes that the NIOSH 5023 method, with some minor enhancements,
provides the most accurate way to assess exposure to asphalt fume. This report and a proposed revision to the current method were presented to NIOSH scientists at meetings in March
and May 1995, at the Petroleum Institutes Forum and at the American Industrial Hygiene
Conference & Exposition, and have been submitted for publication in a peer-review industrial
(50)
hygiene journal
. Additional method development work may well become necessary if
and when the ongoing toxicology research isolates the compounds in the NIOSH laboratory
fume condensates that may be responsible for the dermal carcinogenicity seen in the NIOSH
mouse studies.
7
The Health Effects of Occupational Exposure to Asphalt Fumes:
a review of the available scientific data and on-going industry and government research
IV
Discussion
and Conclusion
I
n view of the recent developments summarized above, it should be no surprise that NIOSH
and ACGIH are in the process of reevaluating their current occupational health guidelines
(51, 52)
for asphalt FUMES.
3
In addition, OSHA will no doubt eventually complete rulemaking
on its 1992 5.0 mg/m proposal, which has been stalled by an intervening court decision.
(53)
The question, then, is how regulators, industry, workers and others should view the emerging
scientific data while the current research proceeds to a conclusion. NIOSH’s existing Criteria
(3)
Document for asphalt fumes, published in 1977, ) establishes an objective and appropriate
framework for that task.
The first step is to examine the available epidemiologic data - the best evidence of human
risk. As noted above, the most recent authoritative review has been conducted by IARC, which
finds that “so far as carcinogenicity of bitumen fumes in concerned, currently available human evidence is inconclusive.“
(25)
The next step is to evaluate the toxicological data, particularly the two NIOSH mouse skin
painting studies of laboratory-generated asphalt fume condensates. As detailed above, the
available scientific data indicates that it is unlikely that the as-yet-unidentified animal carcinogens in NIOSH’s laboratory fume condensates are present in field fumes in significant
concentrations. The crucial question, therefore, is whether the theoretical possibility that
these compounds may be present in field fumes justifies a determination that exposure to
asphalt fumes presents a cancer risk to humans.
On this question, too, the 1977 NIOSH Criteria Document utilizes a sound scientific approach that should guide the evaluation of today’s data. The evidence available in 1977 included data showing “low” or “truce” concentrations in asphalt fumes of B[a]P, a recognized
carcinogen, and several rodent bioassays yielding low to moderate tumorigenicity for whole
asphalts dissolved in solvents and for certain aromatic and saturated fractions of asphalt.
NIOSH called this evidence “cause for concern,” but found it insufficient to warrant a finding
that asphalt fumes are carcinogenic.
Specifically, NIOSH concluded that the mere presence of “trace” concentrations of B[a]P
could not justify a carcinogenicity finding in view of the demonstrated potential for bio(3)
chemical interactions in complex hydrocarbon mixtures such as asphalt. That judgment was
later confirmed in the first NIOSH mouse study, which showed that the dermal carcinogenicity
of laboratory fume condensates in mice is unrelated to B[a]P.
(29,31)
With respect to the bioassay
data available in 1977 NIOSH found these studies inadequate because, among other things,
they involved “exposures unlikely to be faced by U.S. workers.” Acknowledging that fractionating whole asphalts, or diluting them in solvents, can enhance the tumorigenic potential
of the test materials in a fashion unrepresentative of actual worker fume exposures, NIOSH
called for new studies “designed to simulate the exposure potential of a normal work situation."(3)
While enormous strides have been taken since 1977 in our understanding of the chemistry
and toxicology of asphalt fumes, the data available today do not satisfy the scientific criteria
NIOSH established in 1977. We know that field fumes are much different, in composition and
biological characteristics, from the laboratory-generated fume condensates bioassayed in the
NIOSH mouse studies. (3b,37,38) We also know that the agents in NIOSH Fractions B and C that are
responsible for the mouse skin tumors, although not yet identified, are unlikely to be present
in field fumes in anything more than trace concentrations - if they are present at all. The
8
/
0
The Health Effects of Occupational Exposure to Asphalt Fumes:
a review of the available scientific data and on-going industry and government research
available evidence also reveals that field fumes bear a marked resemblance to NIOSH Fraction
A, which showed no evidence of carcinogenicity in over a dozen bioassays conducted in the
(30)
second NIOSH study,
despite the fact that it contained higher concentrations of 3- to 7-ring
PACs and heterocyclics than do field fumes. (36,38) Thus, Fraction A was non-carcinogenic even
though it may well have contained low levels of the unknown agent responsible for the mouse
skin tumors seen in NIOSH's laboratory fume studies.
These considerations, coupled with the inconclusive human data as underscored in the
(10,25)
recent IARC review,
Discussion
and Conclusion
continued
demonstrate that no carcinogenicity finding for asphalt can be justi-
fied at this time. A 1944 review of the chemical and biological data by Dr. Thomas J. Slaga, a
preeminent research toxicologist on the carcinogenicity of complex hydrocarbon materials,
reaches the same conclusion. (54) Nor is there convincing scientific evidence that exposures to
asphalt fumes at current levels in U.S. asphalt operations are associated with a significant risk
(43,44)
of acute pulmonary or other irritation effects.
Nevertheless, as outlined above, the U.S. asphalt industry is committed to filling the existing gaps in the available evidence and developing a sound scientific basis for identifying and
preventing any and all health hazards that may result from occupational asphalt fume exposures. This objective is being vigorously pursued using a variety of scientific and technical tools,
including short term chemical and biological assays, epidemiologic methods, and engineering and
industrial hygiene studies. The industry research, moreover, is proceeding in tandem with parallel
Government programs and in an open dialogue with scientists from both Government and Organized Labor. There is every reason to hope that these research programs will soon bear fruit in
the form of a greatly improved scientific foundation for hazard and risk assessment.
Further information about the available scientific evidence on the health effects of exposure to roofing asphalt fumes and the ongoing research programs is available from any of the
four U.S. asphalt roofing industry associations which have prepared this review:
Asphalt Roofing Manufacturers Association:
6000 Executive Boulevard, Suite
201,
Rockville, MD 20852-3803
Phone: (301) 231-9050, Fax: (301) 881-6572
Roof Coatings Manufacturers Association:
6000 Executive Boulevard, Suite 201, Rockville, MD 20852-3803
Phone:
(301)
230-2501, Fax: (301) 881-6572
Asphalt Institute:
P.O. Box 14052, Lexington, KY 40512
Phone: (606) 288-4960, Fax: (606) 288-4999
National Roofing Contractors Association:
10255 W. Higgins Road, Suite 600, Rosemont, IL 60018
Phone: (708) 299-9070, Fax: (708) 299-1183
9
The Health Effects of Occupational Exposure to Asphalt Fumes:
a review of the available scientific data and on-going industry and government research
References
1.
2.
King RW, Puzinauskas VP, Holdsworth CE, Asphalt Composition and Health Effects: A Critical Review. Washington, DC: American Petroleum Institute, 1984.
Asphalt Institute, Introduction to Asphalt. 8th ed. College Park, MD: Asphalt Institute, 1988 (on
file at OSHA and NIOSH).
3.
U.S. Department of Health, Education and Welfare, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Criteria for a Recommended Standard:
Occupational Exposure to Asphalt Fumes. DHEW (NIOSH) Pub. No . 78-106, NTIS Publication No.
PB-277-333, September 1977.
4.
American Conference of Governmental Industrial Hygienists, Documentation of the Threshold Limit Values and Biological Exposure Indices. 6th ed. Cincinnati, OH: ACGIH, 1991
5.
U.S. Department of Labor, Occupational Safety and Health Administration, Air Contaminants; Proposed Rule. Federal Register 1992; 57:26182-26190.
6.
Radian Corporation, Final Report: Asphalt Industry Cross-Sectional Exposure Assessment Study . Prepared for the Asphalt Institute, July 12, 1991 (on file at OSHA and NIOSH).
7.
Kojola B, An Emerging Issue: Asphalt Fumes. Appl Occup Environ Hyg 1994; 9(5): 323-329.
8.
Chiazze L, Watkins DK, Amsel J, Asphalt and Risk of Cancer in Man. Br. J. Ind. Med. 1991; 48:538-542.
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International Agency for Research on Cancer, Polynuclear Aromatic Compounds, Part 4: Bitumens,
Coal-Tars and Derived Products, Shale-Oils and Soots. IARC Monographs on the Evaluation of the
Carcinogenic Risk of Chemicals to Humans, Volume 35. Lyon, France: IARC, 1985.
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10
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11
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12